Lab 5

The goal of this lab was to become acquainted  with the processes of image mosaicking, band ratioing, and conducting spectral or spatial image enhancement. These processes are important when faced with a situation in which you must collect data from an area that spans across multiple images or you must analyze and interpret the data of an image that may not be clear.

Two image mosaic processes were used and compared against each other to become familiar with the function and to see which process was more useful when stitching images together.

MosaicPro:

I added the images of interest into the MosaicPro tool and selected "Compute Active Area" in the Image Area Options menu. I used "Histogram Matching" to correct the color in order to make a more seamless stitch in the overlapping area. The Overlap Function perameters were set to default in Overlay to set the brightness values to the top image's in the area where they overlap. The end product was more of an unnoticeable seam than the one mosaic made using MosaicExpress. This is because MosaicPro allows you to manipulate more aspects of the mosaicking process.

MosaicExpress:

I experimented with the MosaicExpress tool to create a mosaicked image of the Eau Claire/Chippewa Valley region. This tool successfully created a mosaic without much effort, but because it did not allow you to correct the colors or choose brightness values at the overlay area, the mosaic has a noticeable overlay region and the images do not blend together.

Band Ratioing:

NDVI (Normalized Difference Vegetation Index: NDVI=(NIR-Red)/(NIR+Red)) was performed on an image of Eau Claire in 2011. White portions are a higher value that indicate a higher difference between the NIR and red bands because of differential absorption and reflection. This represents healthy vegetation because photosynthesizers absorb the red light and reflect much of the NIR.

Image Diferencing to Detect Change:

I assessed the pixel differences between 1991 and 2011 in Eau Claire by differencing the images with the Two Input Operators tool in the Two Image Functions option. Only layer 4 was processed. This image's histogram was stretched to be able to incorporate more brightness values in the image and the upper and lower change-no-change threshold values were used to calculate the difference between Eau Claire in 1991 and 2011 in  ModelMaker.